1. Field of the Invention
The present invention relates to a communication system in which an arbitrary number of communication apparatuses form a group to communicate with each other, and the communication apparatus.
2. Description of the Related Art
In a conventional network conference system, for example, terminals constituting the conference transmit and receive data shared by these terminals in real time. That is, each terminal sends information to the server. The server forms new data on the basis of the information from each terminal and transmits the data to each terminal.
In this conventional technique, however, if the number of terminals increases and these terminals transmit and receive shared data more frequently, the load on the server increases. Consequently, a high-speed apparatus is required as the server, and this increases the system cost.
Recently, a spread spectrum communication method has attracted attention as one digital radio communication method. In particular, a frequency hopping spread spectrum communication method is beginning to be used often because the system configuration can be realized relatively easily.
For example, a radio communication system is provided which includes radio apparatuses serving as subsidiary apparatuses and a radio apparatus serving as a master apparatus for managing these subsidiary apparatuses, and performs radio transmission between these apparatuses by using the frequency hopping spread spectrum communication method.
In one system of this sort, each radio apparatus is given a unique identification number (to be referred to as an ID hereinafter), and the communication system is given a unique identification number (to be referred to as a group-ID hereinafter). Radio apparatuses communicate with each other by using their IDs, and multi-address calling is performed by using the group-ID.
Furthermore, some radio apparatuses in a radio communication system sometimes form small groups (subgroups) to communicate with each other. If this is the case, each subgroup is given a subgroup identification number (to be referred to as a subgroup-ID hereafter). Radio apparatuses having the same subgroup-ID can perform multi-address calling (to be referred to as subgroup communication hereinafter) in the subgroup.
In this conventional system, however, the subgroup-IDs of radio apparatuses are preset, so any arbitrary number of radio apparatuses cannot form a new subgroup.